Mono button: Pressing this button forces mono output (both stereo channels carry the same signal). This can be used for checking mono compatibility.

Effect Slots: The Effect Slots can contain effects such as an EQ or a Compressor. Effects processing takes place after volume/pan processing, thus allowing the Master Limiter effect to clip at the correct level.

Level Meter: The Level Meter shows the actual output level (that is the level after applying effects and volume/pan). This means that the distortion takes place when the meter hits the red section.